1. Field of the Invention
The present invention relates to a mobile terminal, for example, typified by a mobile phone, a data reception method for the same, and a program.
2. Description of the Related Art
As a high-speed wireless communication method for a mobile terminal, for example, typified by a mobile phone, cdma2000 1x-EV DO method has been developed recently. The cdma2000 1x-EV DO method is standardized by Association of Radio Industries and Businesses (ARIB) in Std. T64 IS-2000 C. S. 0024 “High Rate Packet Data Air Interface Specification”, specializing in a data communication in contrast with cdma2000 1x method in order to improve a data rate. Note that, in the cdma2000 1x-EV DO method, “evolution data only” is abbreviated to “EV DO”.
In the cdma2000 1x-EV DO method (hereinafter, abbreviated to an “EVDO method”), a configuration of an upward wireless interface (transmission from a mobile terminal to a base station) applies a quadrature phase shift keying (QPSK) as a modulation method and a code division multiple access (CDMA) as a multiplexing method. The configuration is almost similarly to that of the cdma2000 1x method (hereinafter, abbreviated to a “1x method”).
A configuration of a downward wireless interface (transmission from the base station to the mobile terminal) in the EVDO method greatly differs from the 1x method. Namely, the modulation method is applied with QPSK, 8-position quadrature phase shift keying (8PSK), or 16-position phase amplitude modulation (16QAM) depending on a reception status of the mobile terminal. The multiplexing method is applied with time division multiplex access (TDMA), not CDMA.
TDMA divides time into 1/600 second time unit. Only a single mobile terminal (hereinafter, abbreviated to a terminal) can communicate in the unit time. TDMA switches communication of a plurality of terminals every unit time. Consequently, a data communication can be performed with the maximum power for each of terminals, which allows the data communication between terminals to perform with high speed.
The TDMA, in stark contrast with the conventional personal digital cellular (PDC), determines a terminal that communicates in every slot (scheduling) in the base station side.
In the EVDO method, the better a reception status of a terminal side is, the higher reception data can be achieved. Further, depending on the scheduling, the better the reception status is, the more likely a reception slot is assigned. Therefore, the reception status largely affects throughput. The better the reception status is, the higher the throughput can be obtained. This is a great advantage of the EVDO method. It has a further advantage that mix of signals received from a plurality of antennas allows sensitivity to improve.
In the mobile terminal performing high-speed communication such as the EVDO method described above, a variety of improved technologies has been developed.
For example, Japanese Unexamined Patent Publication (Kokai) No. 2002-369247 discloses a technology concerning a slot assignment for utilizing transmission ability of a base station efficiently. Japanese Unexamined Patent Publication (Kokai) No. 2002-344560 discloses a technology optimizing an error rate and a data rate (communication rate) in a downward data communication.
As one of technologies for avoiding influence of phasing to improve a reception status, diversity reception is applied. The diversity reception (antenna diversity) selects or mixes signals received from a plurality of antennas, hence, achieves a reception signal with a strong signal strength at various conditions.
However, the diversity reception requires a plurality of antennas and reception systems. Therefore, power consumes more than that without diversity reception.
Further, in the mobile terminal able to perform the diversity reception, which applies for example, EVDO method, a further reduction of the power consumption has been demanded.